There is a myth that the Capital Beltway is a bypass around Washington. The planners of the "Golden Ring," back in the 1930s and into the '50s, dreamed of a "circumferential" highway around Washington that would preserve our region from the ravages of transient cars and trucks bound for other places.

Not a bad idea. But the myth doesn't square with what has happened since the Beltway opened more than 21 years ago.

Consider volume alone: Planners first projected 20,000 vehicles a day just on the Virginia side. By 1967, only three years after opening, the volume per day was about 62,000 vehicles. Today, 116,000 vehicles a day use the Beltway in Virginia.

The Beltway soon became not so much a high-speed traffic wheel deflecting traffic away from the District's hub as a regional "commuter link" between suburbs, shopping centers and offices around and astride its 65-mile circumference.

Estimates are that 75 percent of the traffic on the Beltway today is "local." At least twice a day the figure is probably higher. Anyone can see it for himself: a mother and her children in a station wagon on their way to a Scout meeting, a neighbor rushing to the airport or maybe you "parked" on the Beltway behind a tractor-trailer wreck.

Tractor-trailer rigs account for about 4 percent of the traffic on the Beltway, but for 16 percent of all Beltway accidents, usually serious ones. In most of these accidents, the tractor-trailer operators improperly change lanes, follow too closely or travel over the speed limit.

We don't need to study this phenomenon to understand it. Just venture onto the Beltway and observe for yourself. Tractor-trailers have been involved in four major accidents on the Beltway just since Aug. 12, and they will be involved in about one accident every 25 hours for the remainder of the year.

It's about time that we control tractor-trailers. Let's restrict their travel on the Beltway to the right lane and limit their speed to 40 mph, as Arthur Morrissette of Interstate Van Lines in Fairfax has recommended. They should also be required to maintain a specified distance between one another, so that traffic can safely enter or exit the Beltway.

One can hear the detractors now: it won't work; it's discriminatory; it will produce a slow-moving steel wall in the right lane that will be a dangerous obstacle to vehicles entering or leaving the Beltway. But spacing and traveling at lower speeds will alleviate this concern.

Yes, the measure is discriminatory in recognizing and dealing with an unsafe condition. We haven't heard a single articulate reason why it won't work.